I do agree with the other responder.
I did take one of the ‘certification’ tests. The reason I did is that I had been studying Pilates for a few years, not to teach but for my own interest, but I found the more I did it the more the principles and practices supported my main discipline, and I wanted to begin to integrate those into some of my classes. I felt that as I had 2 strong complimentary backgrounds, ACE in group ex, and ERYT – 500 in yoga, something like this could be a stopgap measure while I found trainings that matched my needs, especially as I was not interested in teaching the pure thing itself, but rather a variety of what could be called yogalates. But I would never market myself to teach in a Pilates studio until and unless I had stronger credentialing.
The problem is, of course, that while I dislike the phrase ‘portfolio expansion’ as it suggests padding, there is a real need for training classes for people with a base of understanding in complimentary disciplines, as differentiated from those who are beginning. For example, when my husband did medical school he did a program for people who already had a PhD, and which was sped up so they finished in 3 years.
I do understand that to be truly accomplished in a discipline one must study it for years. That is one reason the Yoga Alliance was created: to make sure people who were teaching had a reasonable background of principles and practice, but there should also be a middle ground for those who are not ‘yoginis’, but perhaps practice yoga themselves, and would like to have a way professionally to integrate certain parts of yoga into their cycling, or water aerobics, or other classes. Or yoga instructors who like to add some work on Pilates fundamentals to their exploration of alignment. Or personal trainers who would not market themselves as nutritionists, but need enough dietary information to give general guidance to their clients.
So, if you are going for only one certification, or your first one, you are best advised to go for something with real industry acknowledgement. I know it can get expensive, but in the long run it will be worth it.